The invention relates to a power unit for a hybrid vehicle having a two-cylinder reciprocating piston engine which comprises two pistons guided in two cylinders in a tandem arrangement and two counter-rotating crankshafts connected to the pistons by connecting rods, and having a alternator that can rotate in the opposite direction to the first crankshaft and in the same direction as the second crankshaft. The invention additionally relates to a vehicle having such a power unit. A power unit of the above type is known, for example, from patent WO 2012/056275 A1.
The known power unit has a two-cylinder reciprocating piston engine with counter-rotating crankshafts, which are coupled to each other at their shaft journals by spur gears. The spur gears are in engagement with each other and synchronize the counter-rotating crankshafts. The reciprocating piston engine drives an alternator which is used for electricity generation. The alternator comprises an alternator gear wheel which meshes with one of the two crankshafts. In operation, the alternator rotates in the opposite direction to a first crankshaft and in the same direction as a second crankshaft.
The known power unit is used in particular in a hybrid vehicle, and therefore high running smoothness, low-vibration and a compact design are all important factors. These characteristics are already satisfied by the known power unit. Efforts are nevertheless being made to further improve these properties.